The present invention is directed to rackets manufactured from thermosetting resin-impregnated collimated filaments of glass, carbon or graphite fibers.
The use of fibers and a thermosetting resin is well known in the art. A considerable number of structures have been made by a variety of methods using a plurality of separate lengths of roving and using a hand lay-up of material into or onto stationary compression type molds. Some methods use no tensioning at all, while others use forms of tensioning which are non-balanced, non-maximized and in only part of the frame structure. Some basically wood racket designs use a small amount of the materials mentioned as an interlay or overlay with no tensioning. No case is known where the entire basic frame is made from one single length of roving material, machine wound into a solidly closed loop having a racket configuration and bonded integrally into a solid state of balanced, maximized pretension througout the entire basic filament structure to yield an increased strength with a lower than ever weight of material.
In the racket art it is customary to provide rackets in a great number of separate models varying as to total weight, balance, handle size and shaft stiffness. Despite changing from one racket to another the player very often cannot find a model having the exact combination of the variables to best suit his physique, strength and style of play.
In order to make rackets of adequate strength for muscular strong players by prior art methods, one must use a detrimentally excessive weight of material particularly in the lower head, yoke, shaft and handle portions. Lighter weight rackets in the prior art simply do not have the strength and stiffness necessary for an ideal ball-striking implement. In prior art rackets, the distribution of weight of the material is very poor. For example, in wooden frames, a number of plies or layers are glued together after being curved around to form the oval head. These same layers define the yoke and then merge together at the throat and extend on to form the shaft and integral handle. Cutting out of a given length anywhere along the racket across the entire width will remove the same number of ply pieces of the same weight. Hence, the weight of structural material is seen to be evenly distributed along the rackets length. This is analogous to weight distribution in a steel bar of uniform cross-section. In using this bar as say a nail driving implement, the most effective point of nail impact or "sweet spot" is found at a point two-thirds of the bars length away from the hand-held end. This is a clumsy implement indeed when compared to a proper highly effective energy saving hammer having nearly all of it's weight positioned in the head and evenly around the point of nail impact with no significant amount of ineffective, energy wasting, balance-disturbing excess weight elsewhere.
Despite the availability of the new high specific strength materials, current racket designs still imitate the inefficient wooden racket structures in regard to the bar-like distribution of weight in both single and twin shafted models. Full advantage is not taken of the qualities of the new materials to produce a more efficient ball-driving implement. Bar concept designs produce a "sweet spot" location practically touching the bottom of the head frame material. Hence, the ball must be struck nearer to the center of the head well away from the point-losing, wood-shot sweet spot location. This is safer but much less effective in ball stroking because of the significantly lowered coefficient of restitution or transfer of muscular energy to the ball so far away from the actual sweet spot location.
The "perfect" racket would hypothetically have all of it's weight uniformly distributed around only the periphery of the oval head. The sweet spot would then be located in the exact geometric center of the head. The shaft stiffness would be adjustable to the degree preferred by the player. The shaft would be weightless which, of course, is impossible. However, the lighter that the yoke, shaft and handle can be made, the closer we come to perfect racket balance and maximum ball driving effect from a given expenditure of muscular energy. This is a great boon for lighter muscled, fast moving players.
For best possible results a player's particular needs should be met by adjustment to achieve a suitable combination of the following variables: (a) Total racket weight; (b) Weight balance; (c) Handle size; (d) Shaft stiffness; and (e) Kind of strings and stringing tension. The prior art tries to meet the need by providing a vast and confusing variety of models in different weights with different balances having different handles integral with the frame with different shaft stiffnesses. No dealer can possibly carry every possible combination of these variables in a huge inventory. Therefore, the buyer often cannot find the racket best for his physique and style of play.